Fair Value Measurements and Investments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Sep. 30, 2012
Fair Value, Measurement Inputs, Disclosure [Line Items]
Payments from litigation escrow account-Retrospective Responsibility Plan	$ 4,383	$ 140
Probability of exercise by Visa Europe	40.00%
P/E differential at the time of exercise	1.9x
P/E differential at the time of exercise, ratio	190.00%
Spot price to earnings	21.0x
Spot price to earnings, ratio	2100.00%
Incremental price to earnings differential compared to estimate	2.4x
Incremental price to earnings differential compared to estimate, ratio	240.00%
Incremental probability of exercise by Visa Europe	5.00%
Incremental Assumed Price to Earnings Differential at Time of Exercise	1.0x
Incremental P/E differential at time of exercise, ratio	100.00%
Increase in put option value due to increase in price to earnings differential	84
Increase in put option value due to increase in probability of exercise	18
Other than Temporary Impairment Losses, Investments	15
Equity method investments, reclassified as available-for-sale securities, carrying value	12
Available-for-sale securities, previously classified as equity method Investments, fair value disclosure	57
Available-for-sale securities, previously classified as equity method investments, gross unrealized gains	45
Available-for-sale securities, gross unrealized gains	48		4
Available-for-sale securities, gross unrealized losses	6		1
Fair Value, Measurements, Recurring
Fair Value, Measurement Inputs, Disclosure [Line Items]
Visa Europe put option	145		145
Non Marketable Equity Investments
Fair Value, Measurement Inputs, Disclosure [Line Items]
Non-marketable equity investments	$ 54		$ 86

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13, 19

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.